Flexible sidelink control information periodicity for sidelink semi-persistent scheduling

ABSTRACT

Aspects of the present disclosure provide techniques that help reducing transmission overhead related to sidelink control information (SCI). For example, when a transmitter UE has established a sidelink communication with a receiver UE, the transmitter UE may schedule with at least one semi-persistent scheduling (SPS) process at a first time interval. The transmitter UE may sense whether a resource is available for transmissions to the receiver UE based on decoding an SCI, such as an SCI 0-1 message. The SCI is transmitted at a second time interval that is greater than the first time interval. For example, the second time interval may be a multiple of the first time interval of the at least one SPS process. The second time interval may be flexible and may be increased to reduce the number of SCI messages transmitted in certain time periods in order to reduce communication overhead.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims benefits of and priority to U.S. Provisional Patent Application No. 63/059,378, filed Jul. 31, 2020, which is assigned to the assignee hereof and herein incorporated by reference in its entirety as if fully set forth below and for all applicable purposes.

BACKGROUND Field of the Disclosure

Aspects of the present disclosure relate to wireless communications, and more particularly, to device-to-device sidelink communications.

Description of Related Art

Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, broadcasts, etc. These wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power, etc.). Examples of such multiple-access systems include 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) systems, LTE Advanced (LTE-A) systems, code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single-carrier frequency division multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems, to name a few.

In some examples, a wireless multiple-access communication system may include a number of base stations (BSs), which are each capable of simultaneously supporting communication for multiple communication devices, otherwise known as user equipments (UEs). In an LTE or LTE-A network, a set of one or more base stations may define an eNodeB (eNB). In other examples (e.g., in a next generation, a new radio (NR), or 5G network), a wireless multiple access communication system may include a number of distributed units (DUs) (e.g., edge units (EUs), edge nodes (ENs), radio heads (RHs), smart radio heads (SRHs), transmission reception points (TRPs), etc.) in communication with a number of central units (CUs) (e.g., central nodes (CNs), access node controllers (ANCs), etc.), where a set of one or more DUs, in communication with a CU, may define an access node (e.g., which may be referred to as a BS, 5G NB, next generation NodeB (gNB or gNodeB), transmission reception point (TRP), etc.). A BS or DU may communicate with a set of UEs on downlink channels (e.g., for transmissions from a BS or DU to a UE) and uplink channels (e.g., for transmissions from a UE to BS or DU).

These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. NR (e.g., new radio or 5G) is an example of an emerging telecommunication standard. NR is a set of enhancements to the LTE mobile standard promulgated by 3GPP. NR is designed to better support mobile broadband Internet access by improving spectral efficiency, lowering costs, improving services, making use of new spectrum, and better integrating with other open standards using OFDMA with a cyclic prefix (CP) on the downlink (DL) and on the uplink (UL). To these ends, NR supports beamforming, multiple-input multiple-output (MIMO) antenna technology, and carrier aggregation.

Sidelink communications generally refer to communications between devices (e.g., between UEs). As the demand for mobile broadband access continues to increase, the demand for improvements to sidelink communications increases as well.

SUMMARY

The systems, methods, and devices of the disclosure each have several aspects, no single one of which is solely responsible for its desirable attributes. Without limiting the scope of this disclosure as expressed by the claims that follow, some features will now be discussed briefly. After considering this discussion, and particularly after reading the section entitled “Detailed Description” one will understand how the features of this disclosure provide advantages that include improved device-to-device communications in a wireless network.

Certain aspects of this disclosure provide a method for wireless communications by a transmitter user equipment (UE). The method generally includes establishing a sidelink communication with a receiver UE. The method further includes scheduling with at least one semi-persistent scheduling (SPS) process at a first time interval. The method includes transmitting one or more sidelink control information (SCI) messages to the receiver UE at a second time interval greater than the first time interval; and sensing whether a resource is available for transmissions to the receiver UE based on decoding the one or more SCI messages.

Certain aspects of this disclosure provide a transmitter UE including at least one processor and a memory. The at least one processor and the memory are configured to: establish a sidelink communication with a receiver UE; schedule with at least one semi-persistent scheduling (SPS) process at a first time interval; transmit one or more sidelink control information (SCI) messages to the receiver UE at a second time interval greater than the first time interval; and sense whether a resource is available for transmissions to the receiver UE based on decoding the one or more SCI messages.

Certain aspects of this disclosure provide a transmitter UE for wireless communications. The transmitter UE includes means for establishing a sidelink communication with a receiver UE; means for scheduling with at least one semi-persistent scheduling (SPS) process at a first time interval; means for transmitting one or more sidelink control information (SCI) messages to the receiver UE at a second time interval greater than the first time interval; and means for sensing whether a resource is available for transmissions to the receiver UE based on decoding the one or more SCI messages.

Certain aspects of this disclosure provide a non-transitory computer readable medium storing instructions that when executed by a transmitter user equipment (UE) cause the transmitter UE to: establish a sidelink communication with a receiver UE; schedule with at least one semi-persistent scheduling (SPS) process at a first time interval; transmit one or more sidelink control information (SCI) messages to the receiver UE at a second time interval greater than the first time interval; and sense whether a resource is available for transmissions to the receiver UE based on decoding the one or more SCI messages.

To the accomplishment of the foregoing and related ends, the one or more aspects comprise the features hereinafter fully described and particularly pointed out in the claims. The following description and the appended drawings set forth in detail certain illustrative features of the one or more aspects. These features are indicative, however, of but a few of the various ways in which the principles of various aspects may be employed.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the present disclosure can be understood in detail, a more particular description, briefly summarized above, may be had by reference to aspects, some of which are illustrated in the drawings. It is to be noted, however, that the appended drawings illustrate only certain typical aspects of this disclosure and are therefore not to be considered limiting of its scope, for the description may admit to other equally effective aspects.

FIG. 1 is a block diagram conceptually illustrating an example telecommunications system, in accordance with certain aspects of the present disclosure.

FIG. 2 is a block diagram illustrating an example logical architecture of a distributed radio access network (RAN), in accordance with certain aspects of the present disclosure.

FIG. 3 is a diagram illustrating an example physical architecture of a distributed RAN, in accordance with certain aspects of the present disclosure.

FIG. 4 is a block diagram conceptually illustrating a design of an example base station (BS) and user equipment (UE), in accordance with certain aspects of the present disclosure.

FIGS. 5A and 5B show diagrammatic representations of example vehicle to everything (V2X) systems in accordance with some aspects of the present disclosure.

FIG. 6 illustrates an example allocation of a resource pool for sidelink communications, in accordance with certain aspects of the present disclosure.

FIG. 7 is an example graph showing a cycle time of communication between a controller and a sensor or an actuator, in accordance with certain aspects of the present disclosure.

FIG. 8 illustrates an example connection configuration of a programmable logic controller and two or more sensors or actuators, in accordance with certain aspects of the present disclosure.

FIG. 9A illustrates two modes of sidelink communication.

FIG. 9B illustrates two UEs in sidelink communication, in accordance with certain aspects of the present disclosure.

FIG. 10 illustrates an example sensing window and a resource selection window, in accordance with certain aspects of the present disclosure.

FIG. 11 illustrates example operations for wireless communications by a transmitter UE, in accordance with certain aspects of the present disclosure.

FIG. 12 illustrates example communication from a programmable logic controller to a sensor or an actuator, in accordance with certain aspects of the present disclosure.

FIG. 13 illustrates an example comparison of periodicities of semi-persistent scheduling, sidelink control information, and sensing window, in accordance with certain aspects of the present disclosure.

FIG. 14 illustrates a communications device that may include various components configured to perform the operations illustrated in FIG. 11 , in accordance with certain aspects of the present disclosure.

To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one aspect may be beneficially utilized on other aspects without specific recitation.

DETAILED DESCRIPTION

Aspects of the present disclosure provide apparatus, methods, processing systems, and computer readable mediums for sidelink communications with reduced overhead. For example, a transmitter user equipment (UE) may establish a sidelink communication with a receiver UE and schedule with at least one semi-persistent scheduling (SPS) process at a first time interval (e.g., based on the periodicity or recurring frequency of the SPS). The transmitter UE transmits one or more sidelink control information (SCI) messages to the receiver UE at a second time interval (e.g., at a different periodicity or recurring frequency) and senses whether a resource is available for transmissions to the receiver UE based on decoding the one or more SCI messages. The second time interval is greater than the first time interval. The second time interval may be flexible and may be increased to reduce the number of SCI messages transmitted in certain time periods in order to reduce communication overhead. In some cases, the second time interval is a multiple of the first time interval.

In some aspects, a UE may establish sidelink communications with other UEs under Mode 2 resource allocation via SPS processes. In such cases, the disclosed techniques can reduce periodic control overhead in inter-internet-of-things (inter-IoTs) by flexibly reducing the occurrence of the first stage SCI format 0-1 messages (“SCI 0-1”), in addition to omitting the second stage SCI format 0-2 messages (“SCI 0-2”), as illustrated in various examples discussed below. That is, the SCI 0-1 may have an increased cycle period, or multiple SPS processes may be synchronized with a common SCI 0-1, for reduction of the periodic control overhead while maintaining the same resource sensing functionalities. The flexible SCI 0-1 may be used with or without SCI 0-2, depending on particular application demands.

Sidelink transmitters often rely on SCI 0-1 messages (sent from other UEs) to detect the occupied SPS resources. In some examples, an SCI 0-1 message may accompany every SPS transmission, thus sharing the same periodicity as the SPS transmission. When the content of the SPS transmission is relatively small compared to the size of the SCI 0-1 message, the same periodicity configuration may result in a significant overhead. The disclosed techniques enable reducing the significant overhead by flexibly omitting some of the SCI 0-1 messages while maintaining the same level of resource sensing functionalities.

At a high level, the disclosed techniques provide an increased periodicity (or time interval of each cycle or period) of SCI 0-1 for sidelink SPS. The SCI 0-1 periodicity is carefully increased based on the length of the sensing window and without compromising the detectability of SPS resources. The disclosed techniques may therefore be beneficial to many industrial applications, such as in an internet-of-things (IoT) environment where most transmissions are deterministic and periodic. By increasing SCI 0-1 periodicity for sidelink SPS transmission, the control overhead in such IoT environment can be greatly reduced, and reliability can be improved. In some aspects, the transmissions of SCI 0-1 messages associated with different sidelink SPS processes may be synchronized. For example, when a dedicated resource pool is available for SPS transmissions, synchronizing SCI 0-1 messages leads to a better control of the overhead incurred from SPS transmissions.

The following description provides examples, and is not limiting of the scope, applicability, or examples set forth in the claims. Changes may be made in the function and arrangement of elements discussed without departing from the scope of the disclosure. Various examples may omit, substitute, or add various procedures or components as appropriate. For instance, the methods described may be performed in an order different from that described, and various steps may be added, omitted, or combined. Also, features described with respect to some examples may be combined in some other examples. For example, an apparatus may be implemented or a method may be practiced using any number of the aspects set forth herein. In addition, the scope of the disclosure is intended to cover such an apparatus or method that is practiced using other structure, functionality, or structure and functionality in addition to, or other than, the various aspects of the disclosure set forth herein. It should be understood that any aspect of the disclosure disclosed herein may be embodied by one or more elements of a claim. The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any aspect described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects.

The techniques described herein may be used for various wireless communication technologies, such as LTE, CDMA, TDMA, FDMA, OFDMA, SC-FDMA and other networks. The terms “network” and “system” are often used interchangeably. A CDMA network may implement a radio technology such as Universal Terrestrial Radio Access (UTRA), cdma2000, etc. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. cdma2000 covers IS-2000, IS-95 and IS-856 standards. A TDMA network may implement a radio technology such as Global System for Mobile Communications (GSM). An OFDMA network may implement a radio technology such as NR (e.g. 5G RA), Evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDMA, etc. UTRA and E-UTRA are part of Universal Mobile Telecommunication System (UMTS).

New Radio (NR) is an emerging wireless communications technology under development in conjunction with the 5G Technology Forum (5GTF). 3GPP Long Term Evolution (LTE) and LTE-Advanced (LTE-A) are releases of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A and GSM are described in documents from an organization named “3rd Generation Partnership Project” (3GPP). cdma2000 and UMB are described in documents from an organization named “3rd Generation Partnership Project 2” (3GPP2). The techniques described herein may be used for the wireless networks and radio technologies mentioned above as well as other wireless networks and radio technologies. For clarity, while aspects may be described herein using terminology commonly associated with 3G and/or 4G wireless technologies, aspects of the present disclosure can be applied in other generation-based communication systems, such as 5G and later, including NR technologies.

New radio (NR) access (e.g., 5G technology) may support various wireless communication services, such as enhanced mobile broadband (eMBB) targeting wide bandwidth (e.g., 80 MHz or beyond), millimeter wave (mmW) targeting high carrier frequency (e.g., 25 GHz or beyond), massive machine type communications MTC (mMTC) targeting non-backward compatible MTC techniques, and/or mission critical targeting ultra-reliable low-latency communications (URLLC). These services may include latency and reliability requirements. These services may also have different transmission time intervals (TTI) to meet respective quality of service (QoS) requirements. In addition, these services may co-exist in the same subframe.

FIG. 1 illustrates an example wireless communication network 100 in which aspects of the present disclosure may be performed. The wireless communication network 100 may include one or more UEs 120. For example, one or more UEs 120 a of FIG. 1 may be configured to perform operations 1100 described below with reference to FIG. 11 to sense resources using SCI at a reduced, flexible, occurrence frequency (i.e., an extended time interval).

As illustrated in FIG. 1 , the wireless communication network 100 may include a number of base stations (BSs) 110 a-z (each also individually referred to herein as BS 110 or collectively as BSs 110) and other network entities. In aspects of the present disclosure, a roadside service unit (RSU) may be considered a type of BS, and a BS 110 may be referred to as an RSU. A BS 110 may provide communication coverage for a particular geographic area, sometimes referred to as a “cell”, which may be stationary or may move according to the location of a mobile BS 110. In some examples, the BSs 110 may be interconnected to one another and/or to one or more other BSs or network nodes (not shown) in wireless communication network 100 through various types of backhaul interfaces (e.g., a direct physical connection, a wireless connection, a virtual network, or the like) using any suitable transport network. In the example shown in FIG. 1 , the BSs 110 a, 110 b and 110 c may be macro BSs for the macro cells 102 a, 102 b and 102 c, respectively. The BS 110 x may be a pico BS for a pico cell 102 x. The BSs 110 y and 110 z may be femto BSs for the femto cells 102 y and 102 z, respectively. ABS may support one or multiple cells. The BSs 110 communicate with user equipment (UEs) 120 a-y (each also individually referred to herein as UE 120 or collectively as UEs 120) in the wireless communication network 100. The UEs 120 (e.g., 120 x, 120 y, etc.) may be dispersed throughout the wireless communication network 100, and each UE 120 may be stationary or mobile.

According to certain aspects, the UEs 120 may be configured to determine resources to use for sidelink communications (with another UE). As shown in FIG. 1 , the UE 120 a includes a sidelink manager 122. The sidelink manager 122 may be configured to transmit a sidelink communication to another UE, in accordance with aspects of the present disclosure.

Wireless communication network 100 may also include relay stations (e.g., relay station 110 r), also referred to as relays or the like, that receive a transmission of data and/or other information from an upstream station (e.g., a BS 110 a or a UE 120 r) and sends a transmission of the data and/or other information to a downstream station (e.g., a UE 120 or a BS 110), or that relays transmissions between UEs 120, to facilitate communication between devices.

A network controller 130 may couple to a set of BSs 110 and provide coordination and control for these BSs 110. The network controller 130 may communicate with the BSs 110 via a backhaul. The BSs 110 may also communicate with one another (e.g., directly or indirectly) via wireless or wireline backhaul.

The UEs 120 (e.g., 120 x, 120 y, etc.) may be dispersed throughout the wireless communication network 100, and each UE may be stationary or mobile. A UE may also be referred to as a mobile station, a terminal, an access terminal, a subscriber unit, a station, a Customer Premises Equipment (CPE), a cellular phone, a smart phone, a personal digital assistant (PDA), a wireless modem, a wireless communication device, a handheld device, a laptop computer, a cordless phone, a wireless local loop (WLL) station, a tablet computer, a camera, a gaming device, a netbook, a smartbook, an ultrabook, an appliance, a medical device or medical equipment, a biometric sensor/device, a wearable device such as a smart watch, smart clothing, smart glasses, a smart wrist band, smart jewelry (e.g., a smart ring, a smart bracelet, etc.), an entertainment device (e.g., a music device, a video device, a satellite radio, etc.), a vehicular component or sensor, a smart meter/sensor, industrial manufacturing equipment, a global positioning system device, or any other suitable device that is configured to communicate via a wireless or wired medium. Some UEs may be considered machine-type communication (MTC) devices or evolved MTC (eMTC) devices. MTC and eMTC UEs include, for example, robots, drones, remote devices, sensors, meters, monitors, location tags, etc., that may communicate with a BS, another device (e.g., remote device), or some other entity. A wireless node may provide, for example, connectivity for or to a network (e.g., a wide area network such as Internet or a cellular network) via a wired or wireless communication link. Some UEs may be considered Internet-of-Things (IoT) devices, which may be narrowband IoT (NB-IoT) devices.

Certain wireless networks (e.g., LTE) utilize orthogonal frequency division multiplexing (OFDM) on the downlink and single-carrier frequency division multiplexing (SC-FDM) on the uplink. OFDM and SC-FDM partition the system bandwidth into multiple (K) orthogonal subcarriers, which are also commonly referred to as tones, bins, etc. Each subcarrier may be modulated with data. In general, modulation symbols are sent in the frequency domain with OFDM and in the time domain with SC-FDM. The spacing between adjacent subcarriers may be fixed, and the total number of subcarriers (K) may be dependent on the system bandwidth. For example, the spacing of the subcarriers may be 15 kHz and the minimum resource allocation (called a “resource block” (RB)) may be 12 subcarriers (or 180 kHz). Consequently, the nominal Fast Fourier Transfer (FFT) size may be equal to 128, 256, 512, 1024 or 2048 for system bandwidth of 1.25, 2.5, 5, 10, or 20 megahertz (MHz), respectively. The system bandwidth may also be partitioned into subbands. For example, a subband may cover 1.08 MHz (i.e., 6 resource blocks), and there may be 1, 2, 4, 8, or 16 subbands for system bandwidth of 1.25, 2.5, 5, 10 or 20 MHz, respectively.

While aspects of the examples described herein may be associated with LTE technologies, aspects of the present disclosure may be applicable with other wireless communications systems, such as NR. NR may utilize OFDM with a CP on the uplink and downlink and include support for half-duplex operation using TDD. Beamforming may be supported and beam direction may be dynamically configured. MIMO transmissions with precoding may also be supported. MIMO configurations in the DL may support up to 8 transmit antennas with multi-layer DL transmissions up to 8 streams and up to 2 streams per UE. Multi-layer transmissions with up to 2 streams per UE may be supported. Aggregation of multiple cells may be supported with up to 8 serving cells.

In some examples, access to the air interface may be scheduled. A scheduling entity (e.g., a BS) allocates resources for communication among some or all devices and equipment within its service area or cell. The scheduling entity may be responsible for scheduling, assigning, reconfiguring, and releasing resources for one or more subordinate entities. That is, for scheduled communication, subordinate entities utilize resources allocated by the scheduling entity. Base stations are not the only entities that may function as a scheduling entity. In some examples, a UE may function as a scheduling entity and may schedule resources for one or more subordinate entities (e.g., one or more other UEs), and the other UEs may utilize the resources scheduled by the UE for wireless communication. In some examples, a UE may function as a scheduling entity in a peer-to-peer (P2P) network, and/or in a mesh network. In a mesh network example, UEs may communicate directly with one another in addition to communicating with a scheduling entity.

In FIG. 1 , a solid line with double arrows indicates desired transmissions between a UE and a serving BS, which is a BS designated to serve the UE on the downlink and/or uplink. A finely dashed line with double arrows indicates interfering transmissions between a UE and a BS.

FIG. 2 illustrates an example logical architecture of a distributed Radio Access Network (RAN) 200, which may be implemented in the wireless communication network 100 illustrated in FIG. 1 . A 5G access node 206 may include an access node controller (ANC) 202. ANC 202 may be a central unit (CU) of the distributed RAN 200. The backhaul interface to the Next Generation Core Network (NG-CN) 204 may terminate at ANC 202. The backhaul interface to neighboring next generation access Nodes (NG-ANs) 210 may terminate at ANC 202. ANC 202 may include one or more TRPs 208 (e.g., cells, BSs, gNBs, etc.).

The TRPs 208 may be a distributed unit (DU). TRPs 208 may be connected to a single ANC (e.g., ANC 202) or more than one ANC (not illustrated). For example, for RAN sharing, radio as a service (RaaS), and service specific AND deployments, TRPs 208 may be connected to more than one ANC. TRPs 208 may each include one or more antenna ports. TRPs 208 may be configured to individually (e.g., dynamic selection) or jointly (e.g., joint transmission) serve traffic to a UE.

The logical architecture of distributed RAN 200 may support fronthauling solutions across different deployment types. For example, the logical architecture may be based on transmit network capabilities (e.g., bandwidth, latency, and/or jitter).

The logical architecture of distributed RAN 200 may share features and/or components with LTE. For example, next generation access node (NG-AN) 210 may support dual connectivity with NR and may share a common fronthaul for LTE and NR.

The logical architecture of distributed RAN 200 may enable cooperation between and among TRPs 208, for example, within a TRP and/or across TRPs via ANC 202. An inter-TRP interface may not be used.

Logical functions may be dynamically distributed in the logical architecture of distributed RAN 200. The Radio Resource Control (RRC) layer, Packet Data Convergence Protocol (PDCP) layer, Radio Link Control (RLC) layer, Medium Access Control (MAC) layer, and a Physical (PHY) layers may be adaptably placed at the DU (e.g., TRP 208) or CU (e.g., ANC 202).

FIG. 3 illustrates an example physical architecture of a distributed RAN 300, according to aspects of the present disclosure. A centralized core network unit (C-CU) 302 may host core network functions. C-CU 302 may be centrally deployed. C-CU 302 functionality may be offloaded (e.g., to advanced wireless services (AWS)), in an effort to handle peak capacity.

A centralized RAN unit (C-RU) 304 may host one or more ANC functions. Optionally, the C-RU 304 may host core network functions locally. The C-RU 304 may have distributed deployment. The C-RU 304 may be close to the network edge.

A DU 306 may host one or more TRPs (Edge Node (EN), an Edge Unit (EU), a Radio Head (RH), a Smart Radio Head (SRH), or the like). The DU may be located at edges of the network with radio frequency (RF) functionality.

FIG. 4 illustrates example components of BS 110 a and UE 120 a (as depicted in FIG. 1 ), which may be used to implement aspects of the present disclosure. For example, antennas 452, processors 466, 458, 464, and/or controller/processor 480 of the UE 120 a may be used to perform the various techniques and methods described herein with reference to FIG. 11 .

At the BS 110 a, a transmit processor 420 may receive data from a data source 412 and control information from a controller/processor 440. The control information may be for the physical broadcast channel (PBCH), physical control format indicator channel (PCFICH), physical hybrid ARQ indicator channel (PHICH), physical downlink control channel (PDCCH), group common PDCCH (GC PDCCH), etc. The data may be for the physical downlink shared channel (PDSCH), etc. The processor 420 may process (e.g., encode and symbol map) the data and control information to obtain data symbols and control symbols, respectively. The processor 420 may also generate reference symbols, e.g., for the primary synchronization signal (PSS), secondary synchronization signal (SSS), and cell-specific reference signal (CRS). A transmit (TX) multiple-input multiple-output (MIMO) processor 430 may perform spatial processing (e.g., precoding) on the data symbols, the control symbols, and/or the reference symbols, if applicable, and may provide output symbol streams to the modulators (MODs) 432 a through 432 t. Each modulator 432 may process a respective output symbol stream (e.g., for OFDM, etc.) to obtain an output sample stream. Each modulator may further process (e.g., convert to analog, amplify, filter, and upconvert) the output sample stream to obtain a downlink signal. Downlink signals from modulators 432 a through 432 t may be transmitted via the antennas 434 a through 434 t, respectively.

At the UE 120 a, the antennas 452 a through 452 r may receive the downlink signals from the base station 110 a and may provide received signals to the demodulators (DEMODs) in transceivers 454 a through 454 r, respectively. Each demodulator 454 may condition (e.g., filter, amplify, downconvert, and digitize) a respective received signal to obtain input samples. Each demodulator may further process the input samples (e.g., for OFDM, etc.) to obtain received symbols. A MIMO detector 456 may obtain received symbols from all the demodulators 454 a through 454 r, perform MIMO detection on the received symbols if applicable, and provide detected symbols. A receive processor 458 may process (e.g., demodulate, deinterleave, and decode) the detected symbols, provide decoded data for the UE 120 a to a data sink 460, and provide decoded control information to a controller/processor 480.

On the uplink, at UE 120 a, a transmit processor 464 may receive and process data (e.g., for the physical uplink shared channel (PUSCH)) from a data source 462 and control information (e.g., for the physical uplink control channel (PUCCH) from the controller/processor 480. The transmit processor 464 may also generate reference symbols for a reference signal (e.g., for the sounding reference signal (SRS)). The symbols from the transmit processor 464 may be precoded by a TX MIMO processor 466 if applicable, further processed by the demodulators in transceivers 454 a through 454 r (e.g., for SC-FDM, etc.), and transmitted to the base station 110 a. At the BS 110 a, the uplink signals from the UE 120 a may be received by the antennas 434, processed by the modulators 432, detected by a MIMO detector 436 if applicable, and further processed by a receive processor 438 to obtain decoded data and control information sent by the UE 120 a. The receive processor 438 may provide the decoded data to a data sink 439 and the decoded control information to the controller/processor 440.

The controllers/processors 440 and 480 may direct the operation at the BS 110 a and the UE 120 a, respectively. The processor 440 and/or other processors and modules at the BS 110 a may perform or direct the execution of processes for the techniques described herein. As shown in FIG. 2 , the controller/processor 480 of the UE 120 a has a sidelink manager 481 that may be configured for transmitting a sidelink communication to another UE. Although shown at the controller/processor 480 and controller/processor 440, other components of the UE 120 a and BS 110 a may be used performing the operations described herein. The memories 442 and 482 may store data and program codes for BS 110 a and UE 120 a, respectively. A scheduler 444 may schedule UEs for data transmission on the downlink, sidelink, and/or uplink.

In some circumstances, two or more subordinate entities (e.g., UEs) may communicate with each other using sidelink signals. Real-world applications of such sidelink communications may include public safety, proximity services, UE-to-network relaying, vehicle-to-vehicle (V2V) communications, Internet of Everything (IoE) communications, IoT communications, mission-critical mesh, and/or various other suitable applications. Generally, a sidelink signal may refer to a signal communicated from one subordinate entity (e.g., UE1) to another subordinate entity (e.g., UE2) without relaying that communication through the scheduling entity (e.g., UE or BS), even though the scheduling entity may be utilized for scheduling and/or control purposes. In some examples, the sidelink signals may be communicated using a licensed spectrum (unlike wireless local area networks (WLANs), which typically use an unlicensed spectrum).

FIGS. 5A and 5B show diagrammatic representations of example vehicle to everything (V2X) systems in accordance with some aspects of the present disclosure. For example, the vehicles shown in FIGS. 5A and 5B may communicate via sidelink channels and may perform sidelink CSI reporting as described herein.

The V2X systems, provided in FIGS. 5A and 5B provide two complementary transmission modes. A first transmission mode, shown by way of example in FIG. 5A, involves direct communications (for example, also referred to as side link communications) between participants in proximity to one another in a local area. A second transmission mode, shown by way of example in FIG. 5B, involves network communications through a network, which may be implemented over a Uu interface (for example, a wireless communication interface between a radio access network (RAN) and a UE).

Referring to FIG. 5A, a V2X system 500 (for example, including vehicle-to-vehicle (V2V) communications) is illustrated with two vehicles 502, 504. The first transmission mode allows for direct communication between different participants in a given geographic location. As illustrated, a vehicle can have a wireless communication link 506 with an individual (i.e., vehicle to person (V2P), for example, via a UE) through a PC5 interface. Communications between the vehicles 502 and 504 may also occur through a PC5 interface 508. In a like manner, communication may occur from a vehicle 502 to other highway components (for example, roadside service unit 510), such as a traffic signal or sign (i.e., vehicle to infrastructure (V2I)) through a PC5 interface 512. With respect to each communication link illustrated in FIG. 5A, two-way communication may take place between elements, therefore each element may be a transmitter and a receiver of information. The V2X system 500 may be a self-managed system implemented without assistance from a network entity. A self-managed system may enable improved spectral efficiency, reduced cost, and increased reliability as network service interruptions do not occur during handover operations for moving vehicles. The V2X system may be configured to operate in a licensed or unlicensed spectrum, thus any vehicle with an equipped system may access a common frequency and share information. Such harmonized/common spectrum operations allow for safe and reliable operation.

FIG. 5B shows a V2X system 550 for communication between a vehicle 552 and a vehicle 554 through a network entity 556. These network communications may occur through discrete nodes, such as a base station (for example, an eNB or gNB), that sends and receives information to and from (for example, relays information between) vehicles 552, 554. The network communications through vehicle to network (V2N) links 558 and 510 may be used, for example, for long-range communications between vehicles, such as for communicating the presence of a car accident a distance ahead along a road or highway. Other types of communications may be sent by the node to vehicles, such as traffic flow conditions, road hazard warnings, environmental/weather reports, and service station availability, among other examples. Such data can be obtained from cloud-based sharing services.

In some circumstances, two or more subordinate entities (for example, UEs) may communicate with each other using sidelink signals. As described above, V2V and V2X communications are examples of communications that may be transmitted via a sidelink. When a UE is transmitting a sidelink communication on a sub-channel of a frequency band, the UE is typically unable to receive another communication (e.g., another sidelink communication from another UE) in the frequency band. Other applications of sidelink communications may include public safety or service announcement communications, communications for proximity services, communications for UE-to-network relaying, device-to-device (D2D) communications, Internet of Everything (IoE) communications, Internet of Things (IoT) communications, mission-critical mesh communications, among other suitable applications.

Generally, a sidelink may refer to a direct link between one subordinate entity (for example, UE1) and another subordinate entity (for example, UE2). As such, a sidelink may be used to transmit and receive a communication (also referred to herein as a “sidelink signal”) without relaying the communication through a scheduling entity (for example, a BS), even though the scheduling entity may be utilized for scheduling or control purposes. In some examples, a sidelink signal may be communicated using a licensed spectrum (unlike wireless local area networks, which typically use an unlicensed spectrum).

Various sidelink channels may be used for sidelink communications, including a physical sidelink discovery channel (PSDCH), a physical sidelink control channel (PSCCH), a physical sidelink shared channel (PSSCH), and a physical sidelink feedback channel (PSFCH). The PSDCH may carry discovery expressions that enable proximal devices to discover each other. The PSCCH may carry control signaling such as sidelink resource configurations and other parameters used for data transmissions, and the PSSCH may carry the data transmissions.

For the operation regarding PSSCH, a UE performs either transmission or reception in a slot on a carrier. A reservation or allocation of transmission resources for a sidelink transmission is typically made on a sub-channel of a frequency band for a period of a slot. NR sidelink supports for a UE a case where all the symbols in a slot are available for sidelink, as well as another case where only a subset of consecutive symbols in a slot is available for sidelink.

PSFCH may carry feedback such as channel state information (CSI) related to a sidelink channel quality. A sequence-based PSFCH format with one symbol (not including AGC training period) may be supported. The following formats may be possible: a PSFCH format based on PUCCH format 2 and a PSFCH format spanning all available symbols for sidelink in a slot.

FIG. 6 is an example of how resources of a common resource pool 600 may be allocated for sidelink communications (broadcast and groupcast device-to-device or D2D) between UEs (e.g., UEs 110 shown in FIG. 1 ). The common resource pool 600 includes slots 610, 620, and 630 (also referred to as slots 0, 1, and 2). As noted above, with reference to FIGS. 5A and 5B, sidelink generally refers to the link between two users, or user-relays can be used in different scenarios and for different applications. As previously described, when a UE is transmitting a sidelink communication on a sub-channel of a frequency band, the UE is typically unable to receive another communication (e.g., another sidelink communication from another UE) in the frequency band. Thus, sidelink communications may be referred to as being half-duplex. As a result, the UEs 0, 1, and 5, which transmit sidelink communications 612, 614, and 616 respectively, cannot receive the sidelink communications from each other. That is, UE 0 cannot receive the sidelink transmissions 614 and 616. Similarly, UE 2 cannot receive the sidelink transmissions 624 and 632 from UEs 3 and 4, respectively. Also, UE 3 cannot receive sidelink transmission 622 from UE 2, and UE 4 cannot receive the sidelink transmission 634 from UE 2. In aspects of the present disclosure, a sidelink transmission(s) that cannot be received may be referred to as being “erased” for the UE or wireless node that cannot receive the sidelink transmission, because the UE has no information regarding that sidelink transmission. This is unlike other situations in which a UE fails to decode a transmission, because in those situations, the UE may retain some information regarding the transmission that the UE failed to decode, and the UE may combine that retained information with a retransmission that the UE receives to determine the transmission that the UE failed to decode.

According to previously known techniques, resource allocation is reservation based in NR sidelink communications. In these techniques, resource allocations are made in units of sub-channels in the frequency domain and are limited to one slot in the time domain. In the previously known techniques, a transmission may reserve resources in the current slot and in up to two future slots. Reservation information may be carried in sidelink control information (SCI). In the previously known techniques, sidelink control information (SCI) may be transmitted in two stages. A first stage SCI (SCI-1) may be transmitted on a physical sidelink control channel (PSCCH) and contains resource reservation information as well as information needed to decode a second stage SCI (SCI-2). A SCI-2 may be transmitted on the physical sidelink shared channel (PSSCH) and contains information needed to decode data on the shared channel (SCH) and to provide feedback (e.g., acknowledgments (ACKs) or negative acknowledgments (NAKs)) over the physical sidelink feedback channel (PSFCH).

Example Semi Persistent Scheduling Using Flexible Sidelink Control Information

Aspects of the present disclosure provide techniques that help reducing transmission overhead related to sidelink control information (SCI). For example, when a transmitter UE has established a sidelink communication with a receiver UE, the transmitter UE may schedule with at least one semi-persistent scheduling (SPS) process at a first time interval. The transmitter UE may sense whether a resource is available for transmissions to the receiver UE based on decoding an SCI (or one or more SCI messages), such as an SCI 0-1 message. The SCI is transmitted at a second time interval that is greater than the first time interval. For example, the second time interval may be a multiple of the first time interval of the at least one SPS process.

As will be described in greater detail below, in some cases, the second time interval is at least twice as long as the first time interval of the at least one SPS process such that at least one SCI is skipped in one of the at least one SPS process. For example, a physical sidelink shared channel (PSSCH) codeword may be extended to use the symbols previously occupied by the skipped SCI for improving reliability of SPS transmissions. In some cases, the transmitter UE may schedule with two or more SPS processes at different time intervals. The SCI of the two or more SPS processes share the same time resources. The transmitter UE may configure the second time interval such that each of the different time intervals and the second time interval share 1 as an only common divisor, and a multiplication of each of the different time intervals and the second time interval equals to or is less than a sensing time window of the transmitter UE.

Turning to FIG. 7 , an example graph shows a cycle time of communication between a controller (such as a programmable logic controller, “PLC”) and a sensor or an actuator (“S/A”), in accordance with certain aspects of the present disclosure. Both the PLC and the S/A may generally be referred to as UE in this disclosure. In some cases, when the PLC transmits to an actuator, the PLC may be referred to as the transmitter UE, and the S/A may be referred to as the receiver UE. In some cases, when the PLC receives transmissions from a sensor, the PLC may be referred to as the receiver UE, and the S/A may be referred to as the transmitter UE. The designation of the transmitter UE and the receiver UE thus depends on specific operations or circumstances, and is not bound to a device as a permanent or constant attribute.

The communication traffic between the PLC and the S/A (sometimes referred to as mission-critical traffic, for example, when factory automation depends on the traffic) is often deterministic and periodic. As shown in FIG. 7 , the cycle time T_(cyc) includes four components: T_(D-DL), T_(D-UL), and two T_(AP) (i.e., T stands for time). The controller sends a downlink message to the S/A for the period of T_(D-DL). The S/A sends an uplink message to the controller for the period of T_(D-UL). TAP may account for processing times at the S/A upon receiving the downlink message or uplink message.

In aspects, the cycle period T_(cyc) may be of a constant value for cyclic exchanges between PLC and a number of S/As. For example, each PLC may be in sidelink communications with 20 to 50 S/As (or more). In an example industrial environment, a greater number of PLCs (e.g., 100 to 1000, with the actual number scalable to particular applications) may be operating at the same time. Given such large scale configurations, stringent latency and reliability requirements may be imposed onto the PLCs and S/As. For example, the required latency for the communication may be 1-2 ms, with a reliability requirement (error rate) of 10⁻⁶.

Aspects of the present disclosure provide designs for data and control channels to meet such stringent requirements. In addition to the latency and reliability requirements, the sidelink communications between PLCs and S/As may be designed to minimize overhead (e.g., due to various headers in multiple SPS processes), because PLC and S/As often have small application-layer payload, about 40-256 bytes (meaning a larger percentage of a message is overhead).

FIG. 8 illustrates an example connection configuration of a wireless PLC and two or more S/As, in accordance with certain aspects of the present disclosure. As shown, the PLC may communicate with the gNB through a respective Uu-interface and may communicate with S/A1 and S/A2 through sidelink (PC5) interfaces. In some cases, the gNB are ceiling-mounted while the PLCs are located close to machinery in which the S/As are installed. In one beneficial aspect, such wireless connectivity of the PLC and S/As may significantly reduce reconfiguration costs and time on factory floor.

FIG. 9A illustrates two modes of sidelink communications (Mode 1 and Mode 2), which may be applicable to the sidelink communications between PLC and S/As. In Mode 1, the sidelink resources are often scheduled by a gNB. In Mode 2, the UE may autonomously select sidelink resources from a (pre)configured sidelink resource pool(s) based on the channel sensing mechanism. When the UE is in-coverage, a gNB may be configured to adopt Mode 1 or Mode 2. When the UE is out of coverage, only Mode 2 may be adopted.

In Mode 1, the gNB schedules sidelink (SL) resource(s) to be used by UE for SL transmission(s), for example, via dynamic grants (DG), type 1 configured grants (CG) type 1, and/or type w CGs. CG type 1 is activated via radio resource control (RRC) signaling from gNB. DG and CG type 2 are conveyed using downlink control information (DCI) format 3_0 over physical downlink control channel (PDCCH), as shown in FIG. 9B.

In some aspects, the DCI can be a DG and provide allocation to use over sidelink. The DCI can activate/deactivate a CG type 2 for sidelink. The UE reports activation/deactivation confirmation using MAC-CE. For example, the DCI format 3_0 may be used for scheduling of NR PSCCH and PSSCH in one cell. The DCI format 3_0 may include the following information: time gap, HARQ process ID, new data indicator, a lowest index of the subchannel allocation to the initial transmission.

In Mode 2, when traffic arrives at a transmitter UE, the transmitter UE may select resources for PSCCH and PSSCH, and/or reserve resources for retransmissions to minimize latency. Therefore, in conventional configurations the transmitter UE would select resources for PSSCH associated with PSCCH for initial transmission and blind retransmissions, which incurs unnecessary resources and the related power consumption. To avoid such resource waste and other similar resource duplication/blind reservation/redundancy, the UEs in sidelink communication may communicate, as shown in FIG. 9A, to use a subset of the resources. For example, in Mode 2, the UE may determine, (i.e., not scheduled by the gNB) sidelink transmission resource(s) within the sidelink resources configured by the gNB/network (or pre-configured sidelink resources), as further illustrated in FIG. 9B.

Turning to FIG. 9B, two UEs in sidelink communication are shown: the transmitter UE may send PSCCH and PSSCH to the receiver UE. The receiver UE responds by sending sidelink feedback PSFCH to the transmitter UE. In aspects, the transmitter UE senses and selects resources based on SCI 0-1 messages and the reference signal received power (RSRP) measurements of demodulation reference signal (DMRS) inside PSSCH or PSCCH. In some examples, the transmitter UE may use SCI 0-1 or SCI 0-2 to schedule and transmit data through PSSCH. In an example implementation of this disclosure, SCI 0-2 is omitted and SCI 0-1 is flexibly reduced in occurrence frequencies. In case of unicast or groupcast, each receiver UE may send an acknowledgement (ACK) or negative ACK (NACK) using PSFCH upon receiving each transmission.

For example, the SCI 0-1 fields may include: frequency resource assignment, time resource assignment, PSFCH-to-HARQ feedback timing indicator, PUCCH resource indicator, resource reservation period, DMRS pattern, and configuration index (e.g., for CG). SCI 0-1 may occupy 3 bits for priority, 1 bit for the number of DMRS port, 2-4 bits reserved for determination by higher layer parameter (sl-NumReservedBits), among others. The SCI 0-2 is omitted in preferred examples of the present disclosure. When the SCI 0-2 is included, such as for broadcast, unicast, or groupcast, the SCI 0-2 may include a beta_offset indicator, a modulation and coding scheme, a HARQ process ID, among others. Usually, the SCI 0-2 may occupy 1 bit for the new data indicator, 2 bits for redundancy version, 8 bits for source identifier, 16 bits for destination identifier, and 1 bit for CSI request. When the SCI 0-2 field in the corresponding SCI format 0-1 indicates type 1 groupcast, the SCI 0-2 further includes 12 bits for zone identifier, and 4 bits for communication range requirement.

FIG. 10 illustrates an example sensing window and a resource selection window, in accordance with certain aspects of the present disclosure. A UE, in Mode 2 during candidate resource identification or sensing, may determine whether a resource is available or not by decoding SCIs. For example, the UE may measure received power (e.g., RSRP) for reservations in decoded SCIs. As shown, the RSRP of the transmission associated with SCI reserving resources is projected onto the resource selection window. The RSRP may be measured on PSCCH or PSSCH DMRS according to configuration or pre-configuration. The length of the sensing window (where SCI is decoded) may be configured or pre-configured.

FIG. 11 illustrates example operations 1100 for wireless communications by a transmitter UE, in accordance with certain aspects of the present disclosure. For example, operations 1100 may be performed by a UE 120 of FIG. 1 or FIG. 4 when performing sidelink communications with another UE.

Operations 1100 begin, at 1102, by establishing a sidelink communication with a receiver UE. In aspects, establishing the sidelink includes determining a subset of sidelink transmission resources within a set of preconfigured sidelink resources. For example, the sidelink communication may be any device-to-device communications when the transmitter UE and the receiver UE have been configured or are in the process of being configured for the sidelink communication. In some cases, the transmitter UE initiates sidelink communications. In some cases, the transmitter UE enables the receiver UE to initiate sidelink communications. In some cases, establishing a sidelink communication with the receiver UE includes utilizing an existing sidelink connection with the receiver UE.

At 1104, the transmitter UE schedules with at least one semi-persistent scheduling (SPS) process at a first time interval. For example, the at least one SPS process is scheduled in Mode 2 sidelink communications between the transmitter UE and the receiver UE. The SPS process includes using SPS in sidelink Mode 2 resource allocation as discussed herein. In aspects, the first time interval corresponds to a parameter, such as a frequency or periodicity, of the SPS.

At 1106, the transmitter UE transmits one or more sidelink control information (SCI) messages to the receiver UE at a second time interval greater than the first time interval. For example, the second time interval may be a multiple of the first time interval. In some cases, the first time interval corresponds to a periodicity of the SPS process. The second time interval corresponds to a periodicity of the one or more SCI messages. The second time interval may be equal to or is less than a sending time window of the transmitter UE.

At 1108, the transmitter UE senses whether a resource is available for transmissions to the receiver UE based on decoding the one or more SCI messages. By using SPS under Mode 2 resource allocation, periodic control overhead in IoT devices may be reduced by avoiding SCI 0-2 messages.

According to aspects of the present disclosure, SCI 0-1 messages may further be reduced by increasing the time interval of the recurrence of the SCI 0-1 messages, in a flexible manner with respect to the SPS transmission (e.g., not requiring the SCI 0-1 messages to accompany every SPS transmission). This way, the SCI 0-1 messages may be used for detecting occupation status of SPS resources without involving high overhead (e.g., by increasing the second time interval). For example, the second time interval may be greater than the first time interval. In some cases, the second time interval is a multiple of the first time interval.

As noted above, a UE may establish sidelink communications with other UEs under Mode 2 resource allocation via SPS processes. The UEs in sidelink communications may use the same or similar functions presented herein for sensing with flexible SCI time intervals.

In some cases, industry IoT devices use deterministic and periodic transmissions. For such IoT devices, increasing the SCI 0-1 recurrence time interval for sidelink SPS transmission may substantially reduce existing control overhead and improve reliability. In some cases, when a dedicated resource pool is available for SPS transmissions, synchronizing the SCI 0-1 messages may lead to a better control of the overhead incurred from SPS transmissions. Therefore, allowing the second time interval to be flexible with respect to other sidelink UEs (e.g., a third sidelink UE) may allow for the synchronization of SCI 0-1 messages (and the corresponding saving in control overhead of multiple UEs), as discussed below.

In some aspects, the first time interval of the at least one SPS process and the second time interval of the SCI occur periodically. As shown in the scenario 1200 of FIG. 12 , the transmitter UE may be the PLC that sends SPS activation to one or more S/A. The SPS activation is accompanied by SCI 0-1 and data, but is not associated with SCI 0-2. The PLC and one or more S/As have cyclic exchanges therebetween. The SCI 0-1 messages and the following data may include mission-critical traffic that is deterministic and periodic. In some aspects, the SCI 0-1 messages of scenario 1200 may be decoded at the second time interval that equals to or is less than a sensing time window of the transmitter UE. The transmitter UE may determine a periodicity of the SCI 0-1 messages based on the periodicity of the SPS, as further illustrated in FIG. 13 .

FIG. 13 illustrates an example comparison 1300 of periodicities of semi-persistent scheduling, sidelink control information, and a sensing window, in accordance with certain aspects of the present disclosure. In a first general aspect, flexible SCI in SPS may be implemented by extending or increasing the periodicity of SCI 0-1 messages.

For example, as shown in FIG. 13 , the SCI 0-1 message has a period of q×p while the SPS has a period of p, such that at least one SCI is skipped in one of the at least one SPS process. For example, the second time interval is at least twice as long as the first time interval of the at least one SPS process. The period of q×p equals to or is less than the length of the sensing window W for each UE.

The size (duration) of the sensing window W may be preconfigured. The period of the SPS satisfies p≤W. In other words, SCI 0-1 is transmitted for every q SPS transmissions. If q is chosen such that q×p≤W, any sensing window of size W covers at least one SCI 0-1 message corresponding to the sidelink SPS process.

In one illustrative example, when a sidelink SPS has a period p=8, and the observing window size W=50, the maximum q that can be chosen to satisfy q×p≤W is q=6. By selecting q=6, the overhead associated with SCI0-1 is reduced by skipping 5 SCI 0-1 messages that would have accompanied each SPS, while the resource sensing functionalities are maintained because any observing window covers at least one SCI 0-1 message of the sidelink SPS process.

Furthermore, the transmitter UE may extend a PSSCH codeword to use symbols occupied the skipped SCI for improving reliability of SPS transmissions. For example, standard rate-matching method may be used to improve the reliability for SPS transmissions with skipped SCI 0-1 messages by extending the PSSCH codeword to the symbols originally occupied by SCI 0-1 messages.

In some aspects, the SCI messages of the above techniques may include at least two indicators: a first indicator indicating the first time interval of the at least one SPS process, and a second indicator indicating frequency and time resources occupied by the at least one SPS process. The two indicators may be used by other UEs to determine periodic resources occupied by respective SPS processes in corresponding resource selection windows.

In some aspects, the first time interval of the at least one SPS process is indicated in a resource reservation period field of the SCI. For example, the periodicity of the SPS may be indicated in the “Resource Reservation Period” field inside SCI 0-1. The mapping between the indicator and the periodicity may be preconfigured through upper layers.

In some additional aspects, the second indicator is indicated in a frequency resource assignment field and a time resource assignment field of the SCI. For example, the frequency and time resources occupied by the SPS may be indicated in the “Frequency Resource Assignment” and “Time Resource Assignment” fields inside SCI 0-1. The mapping between the indicator and the resource assignments may also be preconfigured through upper layers.

In a second general aspect, SCI 0-1 message transmissions with flexible periodicities may be synchronized or used by multiple SPS processes, such as for multiple sidelink connections with multiple UEs (suppose the number of the multiple UEs is k). The multiple UEs are preconfigured with a same sensing window length W. A dedicated resource pool is provided for sidelink SPS transmissions. These UEs have a set of permitted periodicities {p₁, p₂, . . . , p_(k)} for SPS transmissions using the dedicated resource pool, where max{p₁, p₂, . . . , p_(k)}≤W. The permitted slots for SCI 0-1 transmissions are synchronized across different sidelink SPS processes. The synchronized period of the SCI 0-1 may be selected to be L such that the following conditions are satisfied: (i) L and p_(i) are co-prime (i.e., the greatest common divisor equals 1) and (ii) L×p_(i)≤W for all i=1, 2, . . . , k.

As such, the first condition may ensure that the transmitter UE of a sidelink SPS (that has a period of p_(i), for example) has an opportunity to transmit SCI 0-1 in L×p_(i) slots. The second condition may ensure that any observing window of size W may cover at least one SCI 0-1 message for every sidelink SPS process, to ensure the resource sensing functionalities are maintained while skipping certain SCI 0-1s when possible.

In one illustrative example, when there are three SPS processes that have a set of permitted periods equal to {1, 2, 4}, and the length of sensing window W=12, the periodicity of the synchronized SCI 0-1 transmissions may be defined as 3 to satisfy the two definition conditions—(i) 3 is co-prime with 1, 2, and 4; and (ii) the product of 3 and 1, 2, or 4 is not greater than 12. Consequently, the transmitter UE may transmit the synchronized SCI 0-1 in 3×{1, 2, 4} slots to three SPS processes of different UEs. Standard rate-matching method may also be used to improve the reliability for SPS transmissions with skipped SCI 0-1.

As described above, the two general aspects, when implemented, can therefore reduce transmission overhead in many industrial applications, such as on automated factory floors or in general inter-IoT environment. The first general aspect increases SCI 0-1 periodicity for sidelink SPS transmission, and reduces the number of occurrence of the (one or more) SCI 0-1 message(s). The released space previously occupied by the now skipped SCI 0-1 message may be used to improve reliability and/or to improve payload efficiency. The second general aspect synchronizes SCI 0-1 messages associated with different sidelink SPS processes, such as when a dedicated resource pool is available for SPS transmissions. The synchronized SCI 0-1 messages may provide better control of the overhead incurred in the multiple SPS transmissions, and similarly to improve reliability and/or to improve payload efficiency.

FIG. 14 illustrates a communications device 1400 that may include various components (e.g., corresponding to means-plus-function components) configured to perform operations for the techniques disclosed herein, such as the operations illustrated in FIG. 11 . The communications device 1400 includes a processing system 1402 coupled to a transceiver 1408. The transceiver 1408 is configured to transmit and receive signals for the communications device 1400 via an antenna 1410, such as the various signals as described herein. The processing system 1402 may be configured to perform processing functions for the communications device 1400, including processing signals received and/or to be transmitted by the communications device 1400.

The processing system 1402 includes a processor 1404 coupled to a computer-readable medium/memory 1412 via a bus 1406. In certain aspects, the computer-readable medium/memory 1412 is configured to store instructions (e.g., computer-executable code) that when executed by the processor 1404, cause the processor 1404 to perform the operations illustrated in FIG. 11 . In certain aspects, computer-readable medium/memory 1412 stores code 1414 for establishing a sidelink communication with a receiver UE; code 1416 for scheduling with at least one SPS process at a first time interval; code 1417 for transmitting one or more sidelink control information (SCI) messages to the receiver UE at a second time interval greater than the first time interval, and code 1418 for sensing whether a resource is available for transmissions to the receiver UE based on decoding the one or more SCI messages. In certain aspects, the processor 1404 has circuitry configured to implement the code stored in the computer-readable medium/memory 1412. The processor 1404 includes circuitry 1420 for establishing a sidelink communication with a receiver UE; circuitry 1422 for scheduling with at least one SPS process at a first time interval; circuitry 1424 for transmitting one or more SCI messages to the receiver UE at a second time interval greater than the first time interval, and circuitry 1426 for sensing whether a resource is available for transmissions to the receiver UE based on decoding the one or more SCI messages.

Example Aspects

Aspect 1: A method for wireless communications by a transmitter user equipment (UE), comprising: establishing a sidelink communication with a receiver UE; scheduling with at least one semi-persistent scheduling (SPS) process at a first time interval; transmitting one or more sidelink control information (SCI) messages to the receiver UE at a second time interval greater than the first time interval; and sensing whether a resource is available for transmissions to the receiver UE based on decoding the one or more SCI messages.

Aspect 2: The method of Aspect 1, wherein the second time interval is a multiple of the first time interval.

Aspect 3: The method of Aspect 1 or 2, wherein the second time interval equals to or is less than a sensing time window of the transmitter UE.

Aspect 4: The method of Aspect 3, further comprising determining a periodicity of the one or more SCI messages based on a periodicity of the SPS, wherein the periodicity of the SPS corresponds to the first time interval and the periodicity of the one or more SCI messages corresponds to the second time interval.

Aspect 5: The method of any one of Aspects 1 to 4, wherein the second time interval is at least twice as long as the first time interval of the at least one SPS process such that at least one SCI message is skipped in one of the at least one SPS process.

Aspect 6: The method of Aspect 5, further comprising extending a physical sidelink shared channel (PSSCH) codeword to use symbols occupied by the skipped SCI message for improving reliability of SPS transmissions.

Aspect 7: The method of any one of Aspects 1 to 6, wherein each of the one or more SCI messages includes two indicators: a first indicator indicating the first time interval of the at least one SPS process, and a second indicator indicating frequency and time resources occupied by the at least one SPS process.

Aspect 8: The method of Aspect 7, wherein the two indicators are used by at least a third UE to determine periodic resources occupied by respective SPS processes in corresponding resource selection windows.

Aspect 9: The method of Aspect 7, wherein the first time interval of the at least one SPS process is indicated in a resource reservation period field of one of the one or more SCI messages.

Aspect 10: The method of Aspect 7, wherein the second indicator is indicated in a frequency resource assignment field and a time resource assignment field of one of the one or more SCI messages.

Aspect 11: The method of any one of Aspects 1 to 10, further comprising: scheduling with two or more SPS processes at different time intervals, wherein the SCI of the two or more SPS processes share a same time resources; configuring the second time interval such that (1) each of the different time intervals and the second time interval share “1” as an only common divisor, and (2) a multiplication of each of the different time intervals and the second time interval equals to or is less than a sensing time window of the transmitter UE.

Aspect 12: The method of Aspect 11, wherein the two or more SPS processes are associated with two or more corresponding receiver UEs.

Aspect 13: The method of any one of Aspects 1 to 12, wherein establishing the sidelink comprises determining a subset of sidelink transmission resources within a set of preconfigured sidelink resources.

Aspect 14: The method of Aspect 13, wherein the set of preconfigured sidelink resources is configured by a network entity.

Aspect 15: The method of any one of Aspects 1 to 14, wherein the transmitter UE includes a programmable logic controller (PLC), and wherein the receiver UE includes at least one of: a sensor, or an actuator.

Aspect 16: A transmitter user equipment (UE) comprising at least one processor and a memory configured to: establish a sidelink communication with a receiver UE; schedule with at least one semi-persistent scheduling (SPS) process at a first time interval; transmit one or more sidelink control information (SCI) messages to the receiver UE at a second time interval greater than the first time interval; and sense whether a resource is available for transmissions to the receiver UE based on decoding the one or more SCI messages.

Aspect 17: The transmitter UE of Aspect 16, wherein the second time interval is a multiple of the first time interval.

Aspect 18: The transmitter UE of Aspect 16 or 17, wherein the second time interval equals to or is less than a sensing time window of the transmitter UE.

Aspect 19: The transmitter UE of Aspect 18, wherein the at least one processor and the memory are further configured to: determine a periodicity of the one or more SCI messages based on a periodicity of the SPS, wherein the periodicity of the SPS corresponds to the first time interval and the periodicity of the one or more SCI messages corresponds to the second time interval.

Aspect 20: The transmitter UE of any one of Aspects 16 to 19, wherein the second time interval is at least twice as long as the first time interval of the at least one SPS process such that at least one SCI message is skipped in one of the at least one SPS process; and wherein the at least one processor and the memory are further configured to: extend a physical sidelink shared channel (PSSCH) codeword to use symbols occupied by the skipped SCI message for improving reliability of SPS transmissions.

Aspect 21: The transmitter UE of any one of Aspects 16 to 20, wherein each of the one or more SCI messages includes two indicators: a first indicator indicating the first time interval of the at least one SPS process, and a second indicator indicating frequency and time resources occupied by the at least one SPS process.

Aspect 22: The transmitter UE of Aspect 21, wherein the two indicators are used by at least a third UE to determine periodic resources occupied by respective SPS processes in corresponding resource selection windows.

Aspect 23: The transmitter UE of Aspect 21, wherein the first time interval of the at least one SPS process is indicated in a resource reservation period field of one of the one or more SCI messages.

Aspect 24: The transmitter UE of Aspect 21, wherein the second indicator is indicated in a frequency resource assignment field and a time resource assignment field of one of the one or more SCI messages.

Aspect 25: The transmitter UE of any one of Aspects 16 to 24, wherein the at least one processor and the memory are further configured to: schedule with two or more SPS processes at different time intervals, wherein the SCI of the two or more SPS processes share a same time resources; configure the second time interval such that (1) each of the different time intervals and the second time interval share “1” as an only common divisor, and (2) a multiplication of each of the different time intervals and the second time interval equals to or is less than a sensing time window of the transmitter UE.

Aspect 26: The transmitter UE of Aspect 25, wherein the two or more SPS processes are associated with two or more corresponding receiver UEs.

Aspect 27: The transmitter UE of any one of Aspects 16 to 26, wherein the at least one processor and the memory are configured to establish the sidelink by determining a subset of sidelink transmission resources within a set of preconfigured sidelink resources, wherein the set of preconfigured sidelink resources is configured by a network entity.

Aspect 28: The transmitter UE of any one of Aspects 16 to 27, wherein the transmitter UE includes a programmable logic controller (PLC), and wherein the receiver UE includes at least one of: a sensor, or an actuator.

Aspect 29: A transmitter user equipment (UE) for wireless communications, comprising: means for establishing a sidelink communication with a receiver UE; means for scheduling with at least one semi-persistent scheduling (SPS) process at a first time interval; means for transmitting one or more sidelink control information (SCI) messages to the receiver UE at a second time interval greater than the first time interval; and means for sensing whether a resource is available for transmissions to the receiver UE based on decoding the one or more SCI messages.

Aspect 30: A non-transitory computer readable medium storing instructions that when executed by a transmitter user equipment (UE) cause the transmitter UE to: establish a sidelink communication with a receiver UE; schedule with at least one semi-persistent scheduling (SPS) process at a first time interval; transmit one or more sidelink control information (SCI) messages to the receiver UE at a second time interval greater than the first time interval; and sense whether a resource is available for transmissions to the receiver UE based on decoding the one or more SCI messages.

The methods disclosed herein comprise one or more steps or actions for achieving the methods. The method steps and/or actions may be interchanged with one another without departing from the scope of the claims. In other words, unless a specific order of steps or actions is specified, the order and/or use of specific steps and/or actions may be modified without departing from the scope of the claims.

As used herein, a phrase referring to “at least one of a list of” items refers to any combination of those items, including single members. As an example, “at least one of: a, b, or c” is intended to cover a, b, c, a-b, a-c, b-c, and a-b-c, as well as any combination with multiples of the same element (e.g., a-a, a-a-a, a-a-b, a-a-c, a-b-b, a-c-c, b-b, b-b-b, b-b-c, c-c, and c-c-c or any other ordering of a, b, and c).

As used herein, the term “determining” encompasses a wide variety of actions. For example, “determining” may include calculating, computing, processing, deriving, investigating, looking up (e.g., looking up in a table, a database or another data structure), ascertaining and the like. Also, “determining” may include receiving (e.g., receiving information), accessing (e.g., accessing data in a memory) and the like. Also, “determining” may include resolving, selecting, choosing, establishing and the like.

The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but is to be accorded the full scope consistent with the language of the claims, wherein reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more.” Unless specifically stated otherwise, the term “some” refers to one or more. All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed under the provisions of 35 U.S.C. § 112(f) unless the element is expressly recited using the phrase “means for” or, in the case of a method claim, the element is recited using the phrase “step for.”

The various operations of methods described above may be performed by any suitable means capable of performing the corresponding functions. The means may include various hardware and/or software component(s) and/or module(s), including, but not limited to a circuit, an application specific integrated circuit (ASIC), or processor. Generally, where there are operations illustrated in figures, those operations may have corresponding counterpart means-plus-function components. For example, various operations shown in FIG. 11 may be performed by various processors shown in FIG. 4 , such as processors 466, 458, 464, and/or controller/processor 480 of the UE 120 a.

The various illustrative logical blocks, modules and circuits described in connection with the present disclosure may be implemented or performed with a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device (PLD), discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but in the alternative, the processor may be any commercially available processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

If implemented in hardware, an example hardware configuration may comprise a processing system in a wireless node. The processing system may be implemented with a bus architecture. The bus may include any number of interconnecting buses and bridges depending on the specific application of the processing system and the overall design constraints. The bus may link together various circuits including a processor, machine-readable media, and a bus interface. The bus interface may be used to connect a network adapter, among other things, to the processing system via the bus. The network adapter may be used to implement the signal processing functions of the PHY layer. In the case of a user terminal 120 (see FIG. 1 ), a user interface (e.g., keypad, display, mouse, joystick, etc.) may also be connected to the bus. The bus may also link various other circuits such as timing sources, peripherals, voltage regulators, power management circuits, and the like, which are well known in the art, and therefore, will not be described any further. The processor may be implemented with one or more general-purpose and/or special-purpose processors. Examples include microprocessors, microcontrollers, DSP processors, and other circuitry that can execute software. Those skilled in the art will recognize how best to implement the described functionality for the processing system depending on the particular application and the overall design constraints imposed on the overall system.

If implemented in software, the functions may be stored or transmitted over as one or more instructions or code on a computer readable medium. Software shall be construed broadly to mean instructions, data, or any combination thereof, whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. Computer-readable media include both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. The processor may be responsible for managing the bus and general processing, including the execution of software modules stored on the machine-readable storage media. A computer-readable storage medium may be coupled to a processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. By way of example, the machine-readable media may include a transmission line, a carrier wave modulated by data, and/or a computer readable storage medium with instructions stored thereon separate from the wireless node, all of which may be accessed by the processor through the bus interface. Alternatively, or in addition, the machine-readable media, or any portion thereof, may be integrated into the processor, such as the case may be with cache and/or general register files. Examples of machine-readable storage media may include, by way of example, RAM (Random Access Memory), flash memory, ROM (Read Only Memory), PROM (Programmable Read-Only Memory), EPROM (Erasable Programmable Read-Only Memory), EEPROM (Electrically Erasable Programmable Read-Only Memory), registers, magnetic disks, optical disks, hard drives, or any other suitable storage medium, or any combination thereof. The machine-readable media may be embodied in a computer-program product.

A software module may comprise a single instruction, or many instructions, and may be distributed over several different code segments, among different programs, and across multiple storage media. The computer-readable media may comprise a number of software modules. The software modules include instructions that, when executed by an apparatus such as a processor, cause the processing system to perform various functions. The software modules may include a transmission module and a receiving module. Each software module may reside in a single storage device or be distributed across multiple storage devices. By way of example, a software module may be loaded into RAM from a hard drive when a triggering event occurs. During execution of the software module, the processor may load some of the instructions into cache to increase access speed. One or more cache lines may then be loaded into a general register file for execution by the processor. When referring to the functionality of a software module below, it will be understood that such functionality is implemented by the processor when executing instructions from that software module.

Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared (IR), radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. Disk and disc, as used herein, include compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk, and Blu-ray® disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Thus, in some aspects computer-readable media may comprise non-transitory computer-readable media (e.g., tangible media). In addition, for other aspects computer-readable media may comprise transitory computer-readable media (e.g., a signal). Combinations of the above should also be included within the scope of computer-readable media.

Thus, certain aspects may comprise a computer program product for performing the operations presented herein. For example, such a computer program product may comprise a computer-readable medium having instructions stored (and/or encoded) thereon, the instructions being executable by one or more processors to perform the operations described herein. For example, instructions for performing the operations described herein and illustrated in FIG. 11 .

Further, it should be appreciated that modules and/or other appropriate means for performing the methods and techniques described herein can be downloaded and/or otherwise obtained by a user terminal and/or base station as applicable. For example, such a device can be coupled to a server to facilitate the transfer of means for performing the methods described herein. Alternatively, various methods described herein can be provided via storage means (e.g., RAM, ROM, a physical storage medium such as a compact disc (CD) or floppy disk, etc.), such that a user terminal and/or base station can obtain the various methods upon coupling or providing the storage means to the device. Moreover, any other suitable technique for providing the methods and techniques described herein to a device can be utilized.

It is to be understood that the claims are not limited to the precise configuration and components illustrated above. Various modifications, changes and variations may be made in the arrangement, operation and details of the methods and apparatus described above without departing from the scope of the claims. 

What is claimed is:
 1. A method for wireless communications by a transmitter user equipment (UE), comprising: establishing a sidelink communication with a receiver UE; scheduling with at least one semi-persistent scheduling (SPS) process at a first time interval; transmitting one or more sidelink control information (SCI) messages to the receiver UE at a second time interval greater than the first time interval; and sensing whether a resource is available for transmissions to the receiver UE based on decoding the one or more SCI messages.
 2. The method of claim 1, wherein the second time interval is a multiple of the first time interval.
 3. The method of claim 1, wherein the second time interval equals to or is less than a sensing time window of the transmitter UE.
 4. The method of claim 3, further comprising determining a periodicity of the one or more SCI messages based on a periodicity of the SPS, wherein the periodicity of the SPS corresponds to the first time interval and the periodicity of the one or more SCI messages corresponds to the second time interval.
 5. The method of claim 1, wherein the second time interval is at least twice as long as the first time interval of the at least one SPS process such that at least one SCI message is skipped in one of the at least one SPS process.
 6. The method of claim 5, further comprising extending a physical sidelink shared channel (PSSCH) codeword to use symbols occupied by the skipped at least one SCI message for improving reliability of SPS transmissions.
 7. The method of claim 1, wherein each of the one or more SCI messages includes two indicators: a first indicator indicating the first time interval of the at least one SPS process, and a second indicator indicating frequency and time resources occupied by the at least one SPS process.
 8. The method of claim 7, wherein the two indicators are used by at least a third UE to determine periodic resources occupied by respective SPS processes in corresponding resource selection windows.
 9. The method of claim 7, wherein the first time interval of the at least one SPS process is indicated in a resource reservation period field of one of the one or more SCI messages.
 10. The method of claim 7, wherein the second indicator is indicated in a frequency resource assignment field and a time resource assignment field of one of the one or more SCI messages.
 11. The method of claim 1, further comprising: scheduling with two or more SPS processes at different time intervals, wherein the SCI of the two or more SPS processes share a same time resources; and configuring the second time interval such that (1) each of the different time intervals and the second time interval share “1” as an only common divisor, and (2) a multiplication of each of the different time intervals and the second time interval equals to or is less than a sensing time window of the transmitter UE.
 12. The method of claim 11, wherein the two or more SPS processes are associated with two or more corresponding receiver UEs.
 13. The method of claim 1, wherein establishing the sidelink comprises determining a subset of sidelink transmission resources within a set of preconfigured sidelink resources.
 14. The method of claim 13, wherein the set of preconfigured sidelink resources is configured by a network entity.
 15. The method of claim 1, wherein the transmitter UE includes a programmable logic controller (PLC), and wherein the receiver UE includes at least one of: a sensor, or an actuator.
 16. A transmitter user equipment (UE) comprising at least one processor and a memory configured to: establish a sidelink communication with a receiver UE; schedule with at least one semi-persistent scheduling (SPS) process at a first time interval; transmit one or more sidelink control information (SCI) messages to the receiver UE at a second time interval greater than the first time interval; and sense whether a resource is available for transmissions to the receiver UE based on decoding the one or more SCI messages.
 17. The transmitter UE of claim 16, wherein the second time interval is a multiple of the first time interval.
 18. The transmitter UE of claim 16, wherein the second time interval equals to or is less than a sensing time window of the transmitter UE.
 19. The transmitter UE of claim 18, wherein the at least one processor and the memory are further configured to: determine a periodicity of the one or more SCI messages based on a periodicity of the SPS, wherein the periodicity of the SPS corresponds to the first time interval and the periodicity of the one or more SCI messages corresponds to the second time interval.
 20. The transmitter UE of claim 16, wherein the second time interval is at least twice as long as the first time interval of the at least one SPS process such that at least one SCI message is skipped in one of the at least one SPS process; and wherein the at least one processor and the memory are further configured to: extend a physical sidelink shared channel (PSSCH) codeword to use symbols occupied by the skipped SCI message for improving reliability of SPS transmissions.
 21. The transmitter UE of claim 16, wherein each of the one or more SCI messages includes two indicators: a first indicator indicating the first time interval of the at least one SPS process, and a second indicator indicating frequency and time resources occupied by the at least one SPS process.
 22. The transmitter UE of claim 21, wherein the two indicators are used by at least a third UE to determine periodic resources occupied by respective SPS processes in corresponding resource selection windows.
 23. The transmitter UE of claim 21, wherein the first time interval of the at least one SPS process is indicated in a resource reservation period field of one of the one or more SCI messages.
 24. The transmitter UE of claim 21, wherein the second indicator is indicated in a frequency resource assignment field and a time resource assignment field of one of the one or more SCI messages.
 25. The transmitter UE of claim 16, wherein the at least one processor and the memory are further configured to: schedule with two or more SPS processes at different time intervals, wherein the SCI of the two or more SPS processes share a same time resources; and configure the second time interval such that (1) each of the different time intervals and the second time interval share “1” as an only common divisor, and (2) a multiplication of each of the different time intervals and the second time interval equals to or is less than a sensing time window of the transmitter UE.
 26. The transmitter UE of claim 25, wherein the two or more SPS processes are associated with two or more corresponding receiver UEs.
 27. The transmitter UE of claim 16, wherein the at least one processor and the memory are configured to establish the sidelink by determining a subset of sidelink transmission resources within a set of preconfigured sidelink resources, wherein the set of preconfigured sidelink resources is configured by a network entity.
 28. The transmitter UE of claim 16, wherein the transmitter UE includes a programmable logic controller (PLC), and wherein the receiver UE includes at least one of: a sensor, or an actuator.
 29. A transmitter user equipment (UE) for wireless communications, comprising: means for establishing a sidelink communication with a receiver UE; means for scheduling with at least one semi-persistent scheduling (SPS) process at a first time interval; means for transmitting one or more sidelink control information (SCI) messages to the receiver UE at a second time interval greater than the first time interval; and means for sensing whether a resource is available for transmissions to the receiver UE based on decoding the one or more SCI messages.
 30. A non-transitory computer readable medium storing instructions that when executed by a transmitter user equipment (UE) cause the transmitter UE to: establish a sidelink communication with a receiver UE; schedule with at least one semi-persistent scheduling (SPS) process at a first time interval; transmit one or more sidelink control information (SCI) messages to the receiver UE at a second time interval greater than the first time interval; and sense whether a resource is available for transmissions to the receiver UE based on decoding the one or more SCI messages. 